Histopathological evaluation of the viability of auto-transplanted ovary following vitrification-thawing process in rabbit as an animal model

Cryopreservation and re-transplantation of ovarian tissue is a relatively new technique to preserve fertility. This study evaluated the preservation of ovarian follicles after the vitrification-thawing procedure by implanting ovarian fragments into the gluteus muscle of rabbit. Bilateral ovariectomy was performed on each rabbit. The cortices were separated from the medullae of ovaries and divided into four fragments. One fresh cortical fragment was used as a control, fixed in 10.00% formalin. Three fragments underwent vitrification-thawing for two weeks. Two of these vitrified-thawed fragments were auto-transplanted into separate locations within the opened gluteus muscle, while the final fragment was fixed in 10.00% formalin. Eight weeks after re-implantation, biopsies were collected from the ovarian fragments and fixed in 10.00% formalin. The numbers and areas (µm2) of morphologically normal follicles were evaluated on sections stained with Hematoxylin and Eosin through light microscopy. The follicular morphology in the ovarian fragments immediately after vitrification-thawing remained similar to that of the fresh ovary. The number of morphologically intact follicles was significantly lower in the ovarian fragments eight weeks after re-implantation than fresh ovary and ovarian tissue fragments after vitrification-thawing procedure. However, follicular development to the antral stage was observed in all samples eight weeks after re-implantation. There was no statistical difference in the areas (µm2) of primordial, primary, pre-antral, and antral follicles in the ovarian fragments before cryopreservation, immediately after vitrification-thawing, and following re-implantation procedures. Auto-transplantation of ovarian tissue into the gluteus muscle of rabbits could be a viable approach for preserving ovarian follicles after vitrification-thawing procedure.